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I operate in a wastewater treatment plant laboratory and I use respirometric method for BOD5 measurement. Recently I am obtaining high value for BOD (biological oxygen demand) for example BOD5 581 mg/L when the COD (chemical oxygen demand) of the same sample 895 mg/L. I did multiple assays on another sample and I obtai... |
There are excellent answers already, but I wanted to address the following question
>[...] how would we mathematically define a normal coordinate for the oxygen(s) and hydrogen during a normal mode vibration of water molecule?
The first step is to switch from cartesian coordinates to internal coordinates. For wat... |
There are excellent answers already, but I wanted to address the following question
>[...] how would we mathematically define a normal coordinate for the oxygen(s) and hydrogen during a normal mode vibration of water molecule?
The first step is to switch from cartesian coordinates to internal coordinates. For wat... |
For a personal project, I have been investigating how I would create modern day things with stone age technology.
I have succeeded in finding ways to create a slew of modern conveniences, but I am getting stuck on NaOH. I feel I am overlooking something obvious.
I realize it can be made from NaHCO3 + Ca(OH)2, but... |
For a personal project, I have been investigating how I would create modern day things with stone age technology.
I have succeeded in finding ways to create a slew of modern conveniences, but I am getting stuck on NaOH. I feel I am overlooking something obvious.
I realize it can be made from NaHCO3 + Ca(OH)2, and... |
@Raphaël did the hard part. ΔH is larger than zero.
>[OP] Since the the solubility increases as the temperature is raised (ΔG∘ becomes more negative), I know that ΔS∘ is positive
This argument linking solubility and Gibbs energy is incorrect. Le Chatelier or the Van't Hoff equation connects the temperature-depend... |
For a personal project, I have been investigating how I would create modern day things with stone age technology.
I have succeeded in finding ways to create a slew of modern conveniences, but I am getting stuck on $\ce{NaOH}$. I feel I am overlooking something obvious.
I realize it can be made from $\ce{NaHCO3 + ... |
Different regions of the electromagnetic spectrum has different activity on matter.
Microwave can induce molecular rotation, Infrared can induce Molecular vibration, Visible and Ultra-violet light can induce electron excitation, and X-ray and Gamma ray can induce ionization.
Is there any activity specific only t... |
I am given an amino acid with an ionizable side chain at a certain pH. How do I determine the net charge of that amino acid when there are mixed protonation states of one or more of the groups at that pH? |
How do I calculate net charge of an amino acid at given pH? |
I am given an amino acid with an ionizable side chain at a certain pH. How do I determine the net charge of that amino acid when there are mixed protonation states of one or more of the groups at that pH (pKa of side chain, for example, is really close to the pH)? |
I am given an amino acid with an ionizable side chain at a certain pH. How do I determine the net charge of that amino acid when there are mixed protonation states of one or more of the groups at that pH (pKa of side chain, for example, is really close to the pH)?
Amino acids have terminal carboxyl and amino groups;... |
How do I calculate the ensemble-average net charge of an amino acid at given pH? |
> Is there a difference in interpretation of dipole moment in Physics and Chemistry?
Addressing the above part: The definition of dipole moment is the same in physics and chemistry. However, the chemist's dipole moment has opposite directions as compared to the physicist. Which one is right? Of course, the physicis... |
Inter-system crossing (ISC) is a radiationless process involving forbidden transitions between singlet and triplet state. These are more common with heavy atom molecules, so I understand that ISC is dependent on the atomic number.
What I don't understand is how does the temperature influence the ISC? |
Why is the iron inter-system crossing non-negligible at high temperatures? |
I think I understand the basics of the electron spin. However, I'm trying to figure out how to tell if, when shooting a beam of atoms (the Stern-Gerlach experiment), how to tell if an element will have some atoms deflecting up and some down?
I initially thought to draw out the electron distribution of each possible el... |
[![enter image description here][1]][1]I think I understand the basics of the electron spin. However, I'm trying to figure out how to tell if, when shooting a beam of atoms (the Stern-Gerlach experiment), how to tell if an element will have some atoms deflecting up and some down?
I initially thought to draw out the el... |
[![enter image description here][1]][1][![enter image description here][2]][2]I think I understand the basics of the electron spin. However, I'm trying to figure out how to tell if, when shooting a beam of atoms (the Stern-Gerlach experiment), how to tell if an element will have some atoms deflecting up and some down?
... |
I have two samples of water- 'A' and 'B'. My thermometer measured them to be 90°C. They both have different volumes. $*$So, the kinetic energy of the particles of sample A and B is same or different? Through this question, i want to ask whether temperature measurement results depend upon how many particles hit the bulb... |
I have two samples of water- 'A' and 'B'. My thermometer measured them to be 90°C. They both have different volumes. $*$So, the kinetic energy of the particles of sample A and B is same or different? Through this question, i want to ask whether temperature measurement results depend upon how many particles hit the bulb... |
I have two samples of water- 'A' and 'B'. My thermometer measured them to be 90°C. They both have different volumes. $*$So, the kinetic energy of the particles of sample A and B is same or different? Through this question, I want to ask whether temperature measurement results depend upon how many particles hit the bulb... |
the question was whether the following compounds have the center of symmetry or not .the question was :
[![enter image description here][1]][1]
And the answer is that there is no center of symmetry .how? according to me, there should be the centre of symmetry. I have made it like this:[
Since this is a cyclic process:- **Change in internal energy=0**.
In the process C-A the work done W is zero, thus the heat Q is zero since it is an isochoric process.
Next in the process A-B, I got the heat Q to be equal to 0.5 L-atm and Work ... |
What is the the total heat extracted in the process? |
Welcome back! Today I would like your help to generate $\ce{SiO2}$ and $\ce{NaSO4}$ from plant ash. This is part 2 of my Gilligan's Island Challenge series. You are stuck on an island with access to a forest, a river, a lake, and a surface vein of coal. For the sake of today's challenge, assume the beach is too far awa... |
We need to extract $\ce{SiO2}$ and $\ce{NaSO4}$ from plant ash. This is part 2 of my Gilligan's Island Challenge series. You are stuck on an island with access to a forest, a river, a lake, and a surface vein of coal. For the sake of today's challenge, assume the beach is too far away to use its sand. Thus, we're going... |
We need to extract $\ce{SiO2}$ and $\ce{NaSO4}$ from plant ash. This is part 2 of my Gilligan's Island Challenge series ([Part 1](https://chemistry.stackexchange.com/questions/120008/primitive-production-of-naoh)). You are stuck on an island with access to a forest, a river, a lake, and a surface vein of coal. For the ... |
We need to produce NaOH with primitive Technology. This is Part 1 of my Gilligan's Island Challenge series ([Part 2](https://chemistry.stackexchange.com/questions/120033/primitive-technology-extract-sio2-na2so3-from-ash)). You are stuck on an island with access to a beach, a forest, a river, a lake, and a surface vein ... |
For an ideal gas, we have
$$C_p - C_V = nR$$
where
$C_p$ is heat capacity at constant pressure,
$C_V$ is heat capacity at constant volume,
$n$ is amount of substance, and
$R=N_\mathrm A\cdot k_\mathrm B=8.314\,462\,618\,153\,24\ \mathrm{J\ mol^{-1}\ K^{-1}}$<sup>[[source](http://physics.nist.gov/cgi-b... |
We need to extract $\ce{SiO2}$ and $\ce{Na2SO4}$ from plant ash. This is part 2 of my Gilligan's Island Challenge series ([Part 1](https://chemistry.stackexchange.com/questions/120008/primitive-production-of-naoh)). You are stuck on an island with access to a forest, a river, a lake, and a surface vein of coal. For the... |
I operate in a wastewater treatment plant laboratory and I use respirometric method for BOD5 measurement (hach direct plus). Recently I am obtaining high value for BOD (biological oxygen demand) for example BOD5 581 mg/L when the COD (chemical oxygen demand) of the same sample 895 mg/L. I did multiple assays on another... |
The textbook the OP references has most of the information: The overall measured dipole moment, the way bond dipoles add up to the molecule dipole, and how to calculate the bond dipole. Also, it states that a proton and an electron at a distance of 100 pm have a dipole moment of 4.80 D. From that information, we should... |
> I have two samples of water – 'A' and 'B'. My thermometer measured them to be 90 °C. They both have different volumes. So, the kinetic energy of the particles of sample A and B is same or different?
The total kinetic energy is different. The average kinetic energy per particle is the same.
> Through this questi... |
> I have two samples of water – 'A' and 'B'. My thermometer measured them to be 90 °C. They both have different volumes. So, the kinetic energy of the particles of sample A and B is same or different?
The total kinetic energy is different. The average kinetic energy per particle is the same.
> Through this questi... |
is 6-benzylhexanoic acid the same as 7-phenylheptanoic acid? If the two compounds stated are equal, what's the more preferred IUPAC name? |
is 6-benzylhexanoic acid the same as 7-phenylheptanoic acid? |
Inter-system crossing (ISC) is a radiationless process involving forbidden transitions between singlet and triplet state. These are more common with heavy atom molecules, so I understand that ISC is dependent on the atomic number.
How does the temperature influence the ISC? Is this related to activation energy? Is t... |
How does [this][1] compound even exist? Having such a massive ring strain.
Is it even conjugated? As it's resonance structure will have all double bonds.
Since it was reported to be found, there must be some stabilizing factor. I was wondering whether that might be aromaticity, since it does have 4n+2 electrons.
... |
Is this compound aromatic? |
Why are the coordination compounds representated by arrows? Is it necessary to write every coordination compounds with the arrow side of the bond facing the metal ion and the other part the ligand? |
Is it important to use arrows as bonds in writing coordination compounds? |
There is a cylinder-piston system with some gas in it, and let's say this system is a closed system.
Say that the system is submerged in a large beaker of water whose temperature is $25^\circ C$. A spark is used to trigger an reaction in the system, and after the reaction is completed, the temperature of the water bat... |
In many text books, it is written that "the value of rate constant depends on, nature of reactant, temperature and catalyst. It is independent of concentration of the reactants".
But unit of rate constant is
$$=[\frac{mol}{litre}]^{1-n} sec^{-1}$$
where n is the order of reaction.
So except first order react... |
A [previous question][1] (April 2017) asked about black $\ce{NiO}$ did not supply any answer. Sadly, such a referral only deters colleagues from commenting on the current question.
There is a great deal of literature on cation defects in non-stoichiometric nickel (II) oxide. There is much on charge-transfer in defec... |
How does [this][1] compound even exist? Having such a massive ring strain.
Is it even conjugated? As it's resonance structure will have all double bonds.
Since it was reported to be found, there must be some stabilizing factor. I was wondering whether that might be aromaticity, since it does have 4n+2 electrons.
... |
Is cyclo[18]carbon aromatic? |
Im confused why P2O5 concentrations are reported for materials which have no P4O10 in them. I guess it simplifies things once you understand it. However, at the moment I don't understand how the conversion is done.
For example. the wiki page: https://en.wikipedia.org/wiki/Phosphoric_acid
States that a P2O5 conc... |
How to convert P2O5 concentration to H3PO4 concentration? |
The [document the OP references][1] has most of the information: The overall measured dipole moment, the way bond dipoles add up to the molecule dipole, and how to calculate the bond dipole. Also, it states that a proton and an electron at a distance of 100 pm have a dipole moment of 4.80 D. From that information, we s... |
Different regions of the electromagnetic spectrum interact differently with matter:
- Microwave radiation can induce molecular rotation.
- Infrared radiation can induce molecular vibration.
- Visible and ultraviolet light can induce electron excitation.
- X-rays and gamma rays can induce ionization.
Is t... |
What are the effects of radio waves on matter? |
I'm confused why P<sub>2</sub>O<sub>5</sub> concentrations are reported for materials which have no P<sub>4</sub>O<sub>10</sub> in them. I guess it simplifies things once you understand it. However, at the moment I don't understand how the conversion is done.
For example. the [Wikipedia page on phosphoric acid][1] s... |
I'm confused why $\ce{P2O5}$ concentrations are reported for materials which have no $\ce{P4O10}$ in them. I guess it simplifies things once you understand it. However, at the moment, I don't understand how the conversion is done.
For example. the [Wikipedia page on phosphoric acid][1] states that a $\ce{P2O5}$ conc... |
I'm confused why $\ce{P2O5}$ concentrations are reported for materials which have no $\ce{P2O5}$ in them. I guess it simplifies things once you understand it. However, at the moment, I don't understand how the conversion is done.
For example. the [Wikipedia page on phosphoric acid][1] states that a $\ce{P2O5}$ conce... |
There is a cylinder-piston system with some gas in it, and let's say this system is a closed system.
Say that the system is submerged in a large beaker of water whose temperature is $25\ \mathrm{^\circ C}$. A spark is used to trigger a reaction in the system, and after the reaction is completed, the temperature of the... |
I thought molecules that have a ring have an added degree of unsaturation, but this explanation has confused me:
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/DeXPe.png
How can something like cyclohexane which has degree of unsaturation of 1, be considered to be "saturated"? Are... |
I know that enolate ion is the anion formed when an alpha hydrogen in the molecule of an aldehyde or ketone is removed as a hudrogen ion .
In the above question I find only two alpha hydrogen which can participate (written with red pen)
The ans for the above question is 3 . But i am able to draw 4 structures :
Where i am getting wrong ?? |
How there are 3 possible tautomers? |
When the process is exothermic (ΔH<sub>system</sub><0), and the entropy of the system increases (ΔS<sub>system</sub>>0), the sign of ΔG<sub>system</sub> is negative at all temperatures. Thus, the process is always spontaneous.
It is easy to prove this using the formula of Gibbs free energy, but how can we prove it ... |
The problem is that in your last wondering, i.e. "wouldn't the system be at a higher temperature because it's 28 C?" is that you're confusing the system and its environment. The system here is the cylinder full of explosive chemical, the environment is the surrounding water. Note that technically, though, there is no r... |
I know the question sounds a bit silly and there are many similar answered questions but my 3D visualization (imagination) is very bad. There are some images of octahedral and tetrahedral holes but still there's no easy explanation. Can someone help me? |
The answer for the above question is 3. But I am able to draw 4 structures:
Where am I getting wrong? |
How there are 3 possible tautomers of 2,2,4-trimethylheptane-3,5-dione? |
I would like to address one of the OP's questions about heat transfer directly because the existing answers did not (yet):
>[OP:] I think that heat is lost by the system since the surrounding(water)'s temperature increased, and work has been done to the system. However, when I consider the thermal equilibrium, the s... |
From studying Beta-oxidation of Free Fatty Acids, I've learned how to compute for the ATP equivalence of Even-Chain and Odd-Chain Free fatty acids.
What really bothers me now is how to compute for the ATP equivalence of an unsaturated fatty acid. Since one of the major difference of the process is in unsaturated fat... |
How to compute for the ATP molecule that can be produced from an unsaturated Free Fatty Acid? |
In many Chemistry books, the dipole moment of molecules is calculated through algebraic formulas. However, another definition of the dipole moment is
$$\vec{\mu} = \sum_i q_i \, \vec{r}_i$$
So, how can we calculate the dipole moment of water, for example using this formula? Is there a difference in interpretatio... |
Let us suppose that we are given two weak bases $HA_1$ and $HA_2$ and we are also given the $K_{A1}$ and $K_{A2}$. How can we calculate the pH of the mixture? |
How do I find pH of a mixture of weak acids? |
Suppose that we are given two weak bases $\ce{HA(1)}$ and $\ce{HA(2)}$. We are also given the $K_\ce{HA(1)}$ and $K_\ce{HA(2)}$. How can we calculate the $\mathrm{pH}$ of the mixture? |
Suppose that we are given two weak bases $\ce{HA_1}$ and $\ce{HA_2}$. We are also given the $K_\ce{HA_1}$ and $K_\ce{HA_2}$. How can we calculate the $\mathrm{pH}$ of the mixture? |
I'm looking to do an experiment involving hot chlorine gas (900 Celsius), however at the moment the only material I'm aware of that could cope with this is Hastelloy's C-22 alloy. What other alternatives exist? |
What materials are resistant to hot chlorine? |
Is it possible to extract magnesium from epsom salt? |
Why are some elements such as phosphorus reported as $\ce{P2O5}$ concentrations when the materials have no $\ce{P2O5}$ in them. I would like an explanation of how the conversion is done between real life and this idealized state.
For example. the [Wikipedia page on phosphoric acid][1] states that a $\ce{P2O5}$ conce... |
Why do the bond dissociation energies of the O-H bonds in water differ? Is it related to an increase in lone pair-bond pair repulsions upon the breaking of the first O-H bond (decrease in stability, so lesser energy is required to break the bond)? |
We need to extract $\ce{SiO2}$ and $\ce{Na2SO4}$ from plant ash. This is part 2 of my Gilligan's Island Challenge series ([Part 1](https://chemistry.stackexchange.com/questions/120008/primitive-production-of-naoh)). You are stuck on an island with access to a forest, a river, a lake, and a surface vein of coal. For the... |
From Atkins' Physical Chemistry 10th, it states that
> The kinetic model is based on three assumptions:
> 1. The gas consists of molecules of mass $m$ in ceaseless random motion obeying the laws of classical mechanics.
> 2. The size of the molecules is negligible, in the sense that their diameters are much small... |
> There will be many molecules collide with the walls and the molecules will hit another molecules after its collision with wall (right?), thus the pressure of the system should be low. How often the collision of what kind happens under what condition?
The collision condition doesn't need to be strictly in Boyle's l... |
We need to extract $\ce{SiO2}$ and $\ce{Na2SO4}$ from plant ash. This is part 2 of my Gilligan's Island Challenge series ([Part 1](https://chemistry.stackexchange.com/questions/120008/primitive-production-of-naoh)). You are stuck on an island with access to a forest, a river, a lake, and a surface vein of coal. For the... |
The answer for the above question is three. But I am able to draw four structures:
Where am I getting it wrong?
|
How are there three possible tautomers of 2,2,4-trimethylheptane-3,5-dione? |
Why aren't chaperones considered catalysts? |
Supposed you are trying to obtain **magnesium metal** from Epsom salt, $\ce{MgSO4.7 H2O}$:
###Is is worth the effort?
Magnesium metal in the form of chips (particle size 4-30 mesh) in decent purity (99.98%) is available from suppliers such as [Sigma-Aldrich](http://www.sigmaaldrich.com/catalog/product/aldrich/25411... |
This morning a workman came by to my newly rented property to fix a few things, among which a *slightly* blocked bathtub drain.
He let some mild water run continuously and he poured down a chemical, and it wasn't before I saw a huge vapor coming out and an intense boiling-like sound, I realized something was wrong. ... |
in your question formulation, you have forgotten to take into account $\ce{H2O2}$ is a weak acid.
The title should rather be:
**Neutralisation between calcium hydroxide and 30% hydrogen peroxide"**
Unless $\ce{Ca(OH)2}$ was in excess over $\ce{H2O2}$ - and it was said it was not - $\mathrm{pH}$ would be always signif... |
in your question formulation, you have forgotten to take into account $\ce{H2O2}$ is a weak acid.
The title should rather be:
**Neutralisation between calcium hydroxide and 30% hydrogen peroxide"**
Unless $\ce{Ca(OH)2}$ was in excess over $\ce{H2O2}$ - and it was said it was not - $\mathrm{pH}$ would be always signif... |
In many textbooks, it is written that:
> The value of rate constant depends on the nature of the reactants, temperature and catalyst. It is independent of the concentration of the reactants.
However, the unit of the rate constant is
$$\left(\frac{\textrm{mol}}{\textrm{litre}}\right)^{1-n} \textrm{sec}^{-1}$$
... |
In the laboratory notes it is indicated that it is ill advised to eat the solid formed from this experiment. An esterification reaction, in which Salicylic acid is treated with acetic anhydride.
If it is for the acid added as catalyst either sulfuric acid or phosphoric acid. Why isn't it possible to neutralize it wi... |
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